Question

need help pzzzzz.....

Answer 1

Formula of R = p *(l/A)
we have to find l = (R*A)/p
Putting values l = 20*πr^2/p
=> 20* π 2.5^2/10*10*100*100*p
=> (20*3.14*6.25)/10^6*1.6*10^-8
=> (392.5)/1.6*10^-2 m
=> (39250)/1.6
=>24531.25 m
=>24.53125km of wire is required .

Answer 2

hello friend....!!!

according to your question it is given that,

• diameter( d ) = 5mm

• resistance ( R) = 20 ohm

• resistivity ( Φ) = 1.6 X 10^-8

now we should find the length of the copper wire,

we know that, R = ΦL / A

implies, Φ = RA / L

implies, L = RA / Φ ---------(1)

to find area,

area = π ( diameter / 2 ) ^2

area = 3.14 ( 5 X 10^-3 / 2 ) ^2

area = 3.14 ( 2.5 X 10^-3)^2

area = 19.6 X 10^-6 ---------( 2)

now substituting equation (2) in (1) gives,

L =( 20 X 19.6x 10^-6 ) / 1.6 X 10^-8

L = 392 / 1.6 X 10^ 2

L = 245 X 10^2 m


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hope it helps....!!!